<!DOCTYPE html>
<html>
<head>
  <meta charset="UTF-8">
  <title></title>
  <style>
    .hezi{
      position: relative;
      display: inline-block;
    }
    .xiala{
      background-color: #4CAF50;
      color:white;
      padding: 16px;
      font-size: 16px;
      border: none;
      cursor: pointer;
    }
    .xiala_hezi{
      display: none;
      position: absolute;
      background-color: #f9f9f9;
      min-width: 160px;
      box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
    }
    .xiala_hezi a{
      color: black;
      padding: 12px 16px;
      text-decoration: none;
      display: block;
    }

    .xiala_hezi a:hover{
      background-color: #f1f1f1;
    }
    .hezi:hover .xiala_hezi{
      display: block;
    }
    .hezi:hover .xiala{
      background-color: #3e8e41;
    }
  </style>
</head>
<body>
<div class="hezi">
  <button class="xiala">下拉菜单</button>
  <div class="xiala_hezi">
    <a href="http://www.runoob.com">菜鸟教程 1</a>
    <a href="http://www.runoob.com">菜鸟教程 2</a>
    <a href="http://www.runoob.com">菜鸟教程 3</a>
  </div>
</div>
</body>
</html>